This invention relates to a nozzle for refining of metals or ferroalloys by blasts of oxygen from above the melt.
An oxygen blast nozzle normally comprises at least one vertical blast pipe for delivering a jet of oxygen for the refining operation. In addition, the blast nozzle may include at least one lateral blast pipe, for delivering a jet of oxygen which is less intense than the primary vertical jet. This lower intensity lateral jet burns the carbon monoxide formed in the course of refining; and creates a surplus of thermal energy (see for example Luxembourg patent LU No. 78 906). Also, the blast nozzle may include a pipe for conveying solid materials suspended in a carrier gas (see for example Luxembourg patent No. 84 433 corresponding to U.S. Pat. No. 4,533,124, which is assigned to the assignee hereof and incorporated herein by reference).
The primary vertical jet of oxygen strikes the surface of the bath, and must possess a sufficient impulse to traverse the bed of slag, or to drive it back, in order to reach the metal melt. It is also necessary for the jet to cause mixing of the slag with the bath, so as to accelerate the metallurgical reactions between these two liquid phases.
The point of impact of the jet on the surface of the bath is fixed; and is positioned substantially at the center of that surface. In order to be better able to distribute the intense heat present at the point of impact, and to intensify the mixing effect, it has long been known that it would be advantageous to be able to displace this point of impact in a controlled manner. Thus, nozzles have been proposed, whose principal axis is inclined, and the entirety of which can oscillate around the vertical axis of the bath. Also known have been nozzle heads whose mouth or opening include mechanical means by which the jet of oxygen can be deflected, these means themselves being movable and remote-controlled.
The disadvantage common to all of these proposed solutions is the need to operate mechanical components which are exposed to high temperatures, large quantities of dust, and the deleterious action of the oxygen. As a result, in almost all steelworks, only conventional blast nozzles with a unidirectional primary jet are to be found.